1. Field of the Invention
The field of this invention lies within the impact printer art. It lies more particularly with regard to impact printers that can place a dot matrix configuration on an underlying media by the impact of a print ribbon which prints on the media such as paper. The dot matrix configuration is provided by a hammerbank having multiple hammers with tips thereon that impact the print ribbon for printing on the paper. Such hammers are known to be retained by permanent magnets which are in associated relationship to the hammers for retaining them through their permanent magnetic force until they are released. Release of the hammers is accomplished by electro-magnetics that overcome the permanent magnetism so that the hammers are fired in a desirable sequence for providing a dot matrix configuration. The release of the hammers through the electro-magnetics is by means of coils which are generally wrapped around pole pieces. This invention specifically relates to the configuration and placement of such coils and pole pieces.
2. Prior Art
Impact printers of the prior art have incorporated banks of hammers with printing tips collectively referred to as a hammerbank. The hammers on the hammerbank are generally mounted in a row along the longitudinal relationship of the hammerbank. Such printers are often specifically referred to as line printers.
Each hammerbank usually has one or more permanent magnets for retaining the hammers until they are fired or released. The retention is generally enhanced by a pole piece or pole pieces which create a magnetic circuit for retaining the hammers in a permanent magnetically retained condition until fired or released by the coils.
The pole pieces are mounted in the hammerbank. They form magnetically oriented circuits to allow for the magnetism from the permanent magnets to be oriented in a manner to pull the hammers back into close contact or in contact with the pole piece ends.
Each pole piece generally has a coil wrapped around it. These pole pieces with their coils are in electro-magnetically connected relationship.
The pole piece windings or coils terminate at certain terminals. The terminals are in turn connected to what are referred to as hammer drivers. These respective hammer drivers are in the form of transistors or other power drivers in order to provide a given current or voltage through the coils to overcome the permanent magnetism. In overcoming the permanent magnetism, the hammers are then released for impact against a ribbon which prints on an underlying media.
The prior art generally has placed pole pieces with their coils such that they are symmetrically placed along the hammerbank. The pole pieces are oftentimes encapsulated in part within a bobbin that constitutes a plastic or other non-conductive material around the pole pieces which in turn can have the coil windings wrapped thereon.
The proximity of the pole pieces with their coils wrapped around them have a limiting effect as to their adjacent placement. In consideration of the fact that it is desirable to have pole pieces as close together as possible while not creating magnetic interference, the symmetrical pole pieces of the prior art have limited the placement. This is because of the fact that when windings around each respective pole piece are placed in adjacent relationship to another pole piece, the thickness of the winding limits the placement. When the windings extend into close proximity with another winding, it is difficult for them to be increased in their dimensions, such as thickness.
The greater number of turns of a given wire gauge provide for greater electromagnetic forces. It is customary to try to optimize the number of windings on each pole piece to the largest practical amount without them interfering either physically or electro-magnetically with another set of windings. The prior art has limited the proximity of the respective windings. When a certain width is reached, it can not be extended any further without displacing the adjacent pole pieces, thereby decreasing the amount of hammers and effectiveness of the hammerbank.
This invention enables greater amounts of wire to be wound around each respective pole piece in closer proximity than in the prior art. To this extent, the windings also with their placement provide less magnetic interaction.
The increased number of coils allows for increased hammers on a hammerbank so that faster printing can take place. The orientation is such where it provides for coil overlapping, staggered displacement, or spatially displaced orientations with regard to the respective coils without increasing the width, spacing, or gaps between the hammers.
Coil losses are generally the bulk of power losses that take place in the drivers as to the power required to drive the coils. With this in mind, when increased winding can be accomplished in the same given space or less space, the power losses decrease. When the power losses decrease, more accurate printing takes place due to the overall rapidity and response of the hammerbanks.
The net result of the invention is that one can use larger gauge wire with fewer windings or lesser gauge wire with greater windings. To the contrary, the increased dimensions of the prior art that cause the pole pieces to be extended from each other or spaced at a further point diminish the overall effectiveness or efficiency of the hammerbanks.
It has been found that in hammerbanks of approximately thirteen and one half (13xc2xd) inches in length, that this invention allows one hundred and twenty six (126) print hammers as opposed to one hundred and two (102) in the same length of the prior art. This is an approximate twenty five percent (25%) increase in the number of hammers creating greater efficiency.
The magnetic efficiency of the hammerbank provides for other benefits. Such benefits can be in the form of eliminating lamination of the pole pieces due to the higher efficiency. Lamination can also be in lesser multiple laminates because the reduced coil losses more than offset any power losses due to eddy currents. In this regard, as to the pole pieces, cheaper materials and construction can be used for the pole pieces thereby decreasing the overall costs while at the same time increasing efficiency.
The invention relies upon the concept of staggering or spatially varying the respective pole pieces and coils. Every other one is in a symmetrically placed manner with the ones in between adopting a different configuration or placement. When adopting this different configuration, the pole pieces allow a greater amount of windings. The windings are placed on the pole pieces so that the coil of one leg is interposed between the coil of the adjacent magnetic circuit.
The geometrical staggering or orientation of orienting windings so that they can be placed in close proximity to each other with less magnetic interference enhances the overall operation of the pole pieces from an electromagnetic standpoint. At the same time the improved magnetics and interposing coils allow for greater spatial density. These improvements will be seen in the specification hereafter.
In summation, this invention comprises a line printer having a hammerbank with a plurality of hammers retained thereon by permanent magnets that are released from the permanent magnets by an improved interposing series of coils wrapped around pole pieces that serve to create a magnetic circuit; each pole piece having a staggered relationship or geometrically offset spatial relationship for establishing greater amounts of windings on each given pole piece.
More specifically, the invention incorporates a hammerbank having a row of hammers mounted thereon. Each of the hammers is retained by permanent magnetism. In order to complete the permanent magnetic circuit, pole pieces are in magnetic orientation to the permanent magnets and the hammers to complete the circuit.
Each of the pole pieces has a winding around it of a given amount of turns. In order to enhance the amount of turns, the pole pieces are staggered or asymmetrically oriented for increased winding between each respective adjacent pole piece. This is accomplished by having one pole piece being spaced from another through a dog leg offset, staggered, removed, or other configuration so that one pole piece can have a winding extending along its length a given distance and amount without interfering with another pole piece. In effect a differing spatial relationship between pole pieces is established to provide for a greater number of turns around each pole piece.
The foregoing orientation between pole pieces can be accomplished by dog legs, offsets, geometric angular orientations, asymmetry, or any other suitable geometry or spatial relationship to maintain a substantial amount of windings in proximity to each other which are greater in number than could be accomplished without the improved geometric orientation.